I agree that it should be removed entirely. It's misleading and confusing and controversial for veteran users of the software, so it's particularly unhelpful to new users.
I don't know that I agree with your interpretation of "two family lines". I understand that as two *ancestral* lines, and a pedigree that's fully populated for a few generations certainly has more than two such lines. In fact, half of the people introduced in each generation backward represent a new line--matrilineal or patrilineal depending on your perspective.